Signaling arrangement for telegraph systems



Oct. 27, 1942.4 R J, EGNER ET AL 2,299,969

' SIGNALING ARRANGEMENT FOR TELEGRAPH SYSTEMS I Filed Dec. 5, 1941 And n 9, w lNyENToRs i 55 JE nel" #mi BY CR, Pr/Iker l z l ATTORNEY Patented Oct. 27, 1942 SIGNALING ARRANGEMENT FOR TELEGRAPH SYSTEMS Robert James Egner, Ridgewood, and Charles Robert Walker, Jersey City, N. J., assignors to American Telephone and Telegraph Company, a corporation of New York Application December 5, 1941, Serial No. 421,718

6 Claims.

This invention relates to telegraph and teletypewriter systems. More particularly, this invention relates to telegraph and teletypewriter systems in which a subscriber connected to the system may be notified this his circuit has been switched into the system so that he may transmit signals thereover.

In telegraph systems where the subscribers station is connected to a central ofiice or central switching point by a line circuit which may be of the open-wire type, voltages induced from power sources and other extraneous sources may become so large as to interfere with signaling over the line circuit. In order to overcome such interference, a separate circuit or conductor, known as a neutralizing circuit or conductor, may be added to the system for the purpose of neutralizing such interfering voltages. In cases Where it is vdesired to notify any particular subscriber that he is connected to another distant subscriber through the central oince or switching point and to keep the subscriber notied continuously that he is so connected, it has heretofore been necessary to provide still a third circuit or conductor over which such auxiliary signals may be transniitted Without in any way interfering with signaling over the line circuit. The addition of this third conductor or circuit is, of course, costly and would add to the maintenance.

According to the present invention it is proposed to obviate the requirement for any such third conductor or circuit by utilizing the neutralizing conductor for auxiliary signaling to the subscriber, thereby indicating to the subscriber than he has or has not been connected to the l system and that his signals are or are not being received over the system.

Another object of this invention is to connect a subscribers station to a central oifice or other switching point by two conductors, (l) a line conductor over which signals may be transmitted and (2) a neutralizing conductor running parallel thereto to substantially reduce the effect of extraneous voltages, and to employ the neutralizing conductor for auxiliary signaling to the subscribers station.

These and other objects of this invention will be better understood from the detailed description hereinafter following, when read in connection with the accompanying drawing showing one embodiment of the invention merely for the purpose of illustration.

Referring to the drawing, there is shown a subscribers oiice at the extreme left at which there is located a sending relay R1 and a receivfil) ing relay R2. The receiving relay R2 includes four windings W1, W2, W3 and W4, which are all approximately of the same number of turns. The winding W1 is connected between the armature of the sending relay R1 and the line circuit or conductor L1-which maybe an open wire line of well-known type-extending between the subscribers ofce and a central office or switching point. The winding W2 is connected between the lower terminal of the winding W1 and the grounded artificial line AL1, the artificial line ALi being employed in a well-known manner to balance the main line conductor or circuit L1. A neutralizing conductor or circlit L2 is connected to the winding W3 of the receiving relay R2 while the artificial line ALz is similarly connected through the winding W4 of relay R2 to the lower terminal of its Winding W3. The articial line AL2 is similar 'to the artificial line AL1 and is employed to ensure that the neutralizing path has the same impedance as the transmission path.

At the central cnice the line circuit L1 is connected to the armature of a relay R3 through the winding W 5 of a relay R4. The artificial line ALs is connected to the winding'Ws of relay R4 for the purpose of balancing the line L1 at the central oflice. The relay R4. also includes windings W7 and W8 which lare similar to windings W5 and Ws, respectively, and a biasing Winding Wg.

In the idle condition of the system the neutralizing wire L2 is connected to the battery B1 at the central ofce by a circuit extending through the contact K1 of the relay R5. This neutralizing wire is associated with a balancing network AL4 which is similar to network ALs at the central office to keep the impedance of the neutralizing path equal to that of the transmission path. In the idle condition of the system, also, the upper winding of the relay R3 is vconnected to the battery B1 through the make-before-break contacts K2 associated with the upper armature of 'relay R5. But during signaling over the system, the relay R5 is operated and therefore the upper Winding of the relay Rs is connected to the upper windings of relays 'Re and R1 over 'acircuit which includes vthe 'upper armature and make Contact of relay R5, the innermost lower armature and make contact of relay R5 and the operating circuit of selector NTS. The lower winding of` the relay R3 is connected to an articial line ALs for balancing purposes.

The selector NTS may be, for example, a nontyping teletypewriter or selector of well-knownI construction. In response 4to a teletypewriter character such as Figures it will close its contact K5, then in response to a subsequent teletypewriter character such as upper case B, it will close its contact K3 momentarily, and later, in response to a third teletypewriter character such as upper case D, it will likewise close its contact K4 momentarily.

The lower windings of the relays Re and R7 are also connected to an artificial line ALs. The apex of the upper and lower windings of relay R7 is connected to the armature of the relay R5. The midpoint of the upper winding of relay R5 is connected to the armature of relay R5 while the midpoint of the lower winding of relay Re is connected to the armature of the relayR7. The two windings of relay Rs are connected to a metallic telegraph line or circuit L3 which may extend to any one of several distant subscribers or offices (not shown), the line La being balanced by a network BN. The selector NTS, when closing its contacts K5 in response to the receipt from line L3 of the teletypewriter character Figures will remain closed thereafter until the receipt of a Letters signal as hereinafter described. The receipt of the teletypewriter character B from line L3 will close the contact K3 for the purpose of operating the relay R5, as will be pointed out hereinafter. The closure of the contacts K4 in response to the teletypewriter character D will operate the relay Re, as will be described hereinafter. The operations of relays R5 and R9 will therefore be controlled by contacts K3 and K4 of selector NTS but the ground for the operating circuits of these relays will be obtained through the contact K5 of the selector. The subsequent receipt of the teletypewriter character Letters from line L3 will restore the selector NTS to its normal position, thereby opening the contact K5. The closing of the contacts K3 or K4 will be ineffective unless the appropriate signal has previously been received to close the selector contact K5.

One of the features oi' the arrangement of this invention is the inclusion at the subscribers o'ice of the relay R10 in series with the neutralizing conductor L2. A lamp and battery may be connected in series with the armature and either the front or back contact of relay R so that the lamp will be lighted either when the relay R10 is energized or when it is deenergized as desired. If desired two lamps P1 and P2 which may be of different colors may be provided as shown in the drawing, one lamp P1 being connected to the.

front contact and the other P2 connected to the back contact of relay R10. To obtain a balanced condition in the line and neutralizing conductors L1 and L2 a similar relay arrangement R11 or an equivalent network, is positioned in series with the line conductor L1. The latter device,r however, need not be a relay but may be any type of network which has the same impedance characteristics as the relay R10.

As will be explained hereinafter the system is so arranged that when the subscribers oice is connected through at the central oiiice to line La, relay R10 will be released and a suitable visual indication will be obtained from the lamp P2. The neutralizing conductor L2 is connected thrcugh contacts K5 of relay R5 to the grounded winding W7 of relay R4 when relay R5 is operated. In that case relay R10 is released because battery B1 is disconnected therefrom at contact K1 of relay R5.

Thus when the subscriber receives an appropriate signal through the medium of lamp P2, it

will indicate that the line L1 is connected to the line L3, thereby enabling him to transmit signals to or receive signals from line La. When this happens the relay R5 will be operated so as to open the contact K1 of relay R5 and then close the contact K5 of relay R5 so as to connect the neutralizing conductor L2 to winding W7 of relay R4. This will cause the release of the relay R10 at the subscribers oice. The lamp P2, after being illuminated, will remain illuminated and indicate that the subscribers set and the c-ircuit connected to line La remain properly coupled together so that signals may be transmitted in both directions over the interconnecting circuits.

When a teletypewriter character such as Figures is received over the line L3, it will be relayed through relay Ra and relays R7 and R5 to the selector NTS, which is connected to positive battery B2 through the make-before-break contacts K7 of relay R5. The receipt of this character will close the platen Contact K5 as already explained. The subsequent receipt of another character such as B over line L3 will cause selector NTS to momentarily close its contacts K3, whereupon the 'relay R5 will be operated over a circuit which includes contacts K5 and K5 of selector NTS, the winding of relay R5, battery B2 and ground. The relay R5 will be locked in its operated position through the back contact of the upper armature of relay R0, the locking circuit including battery B2, the winding of relay R5, the contacts Ks of relay R5, the upper armature and back contact of relay R0 and ground.

By operating relay R5 in response to the receipt of a predetermined character over the line L3, the battery B1-which was previously connected through the make-before-break contacts K2 ofr relay R5 to the upper Winding of relay R3-wi1l be disconnected and the upper winding of relay Ra will be connected to the upper winding of relay R5 over a circuit previously noted. Moreover, the operation of relay R5 will cause the closure of its contacts K5 so as to connect the winding W7 of relay R4 to the neutralizing conductor L2. This will be accompanied by the release of the relay R10 at the subscribers ofce, the extinction of lamp P1 and the illumination of lamp P2. The illumination of lamp P2 will indicate that the connection between line Le and the subscribers ofce has been completed. Signals may then be transmitted between the station connected to the line La (not shown) and the subscribers omce over the line circ-uit L1 in both directions. The neutralizing conductor L2 will at the same time function to substantially reduce, if not entirely overcome, the eiects of power voltages and other extraneous voltages which may be induced into the exposed conductors L1 and L2. The neutralizing conductor L2 will therefore perform two funtions, (l) as a neutralizing conductor to eliminate extraneous voltages and (2) as a medium for indicating to the subscriber through lamp P2 that his circuit is connected through the central office equipment to another subscribers station (not shown) for signaling in the usual way.

The closure of the contacts K3 of the selector NTS is but momentary, as already indicated, in response to the receipt of the teletypewriter lcharacter B. If at some later time the teletypewriter character D is received over the circuit L3, the selector NTS will close its contacts K4 so as to operate the relay R9 provided contact K5 has been previously closed. The operating circuit for relay R9 includes the battery B2, the

winding of relay R9, the contacts Krand K of the selector NTS, and ground. Thev relay Rswill thereafter be locked 1 in its operated position through the contacts K9 of relay R5, the locking circuit including battery B2, the winding of relay R9, the lower armature and make contact of relay R9, the contacts K9 of relay R5, and ground. The operation of relay R9 will also break the locking circuit of relay R5 by opening the back -contact of the upper armature of relay R9 and the relay R5 will then release. The release of relay R5 will in turn bring about the release of relay R9 because the contacts Ks of relay R5 will be opened. Thus upon the receipt of another teletypewriter character such as upper case D, the relay R9 will be operated and then both lrelay R5 and relay Re will shortly thereafter be released.

Upon the release of relay R5 the line L3 will then be disconnected from the line L1 and from the subscribers oiiice connected thereto. The upper winding of relay Rs will then be reconnected to the battery B1 through the make-before-break contact K2 of relay R5. Ihe winding W7 of relay R4 will also be disconnected from the neutralizing conductor L2 by the opening of Contacts Ks of relay R5. The battery B1 will be reconnected through contact K1 of relay R5 to the neutralizing conductor L2, whereupon the relay R will be re-operated to illuminate the lamp P1 at the subscribers office.

It will be apparent that any marking and spacing signals received over line L3 after relay Rs has been operated will move the armature of relay Ra between its marking and spacing contacts M and S to alternately connect the oppositely poled batteries B1 and B2 to the apex of the windings of relay R7. These oppositely poled batteries will then be connected through the upper windings of the relays Rs and R7, through the operating circuit of the selector NTS (not shown) and over the lower innermost armature and make contact of relay R5 to the upper winding of relay R3. The armature of relay Rs will be moved between its marking and spacing contacts in accordance with the signals received from line La and connect corresponding oppositely poled batteries to the line L1 through the winding W5 of relay R4. These oppositely poled voltages will in turn energize the winding W1 of relay R2 f so that the armature of relay R2 will register these marking and spacing signals in a well known manner. During such signaling operations the neutralizing conductor L2 Will function to eliminate extraneous voltages.

In order to send signals from the subscribers office over the lines L1 and L3, the sending relay R1 will be operated in accordance with marking and spacing signals. The armature of relay R1 will connect ground to the line L1 through the Winding W1 of relay R2 for a marking signal and the positive battery B4 to the main line L1 through the same winding of relay R2 for a spacing signal. These marking and spacing signals will then cause currents to ow through the winding W5 of relay R4 in opposite directions so as to move the armature of relay R4 between its marking and spacing contacts M and S. As the armature of relay R4 closes its contacts M and S it will alternately connect oppositely poled batteries to the apex of the windings of relay R3 and thereby transmit oppositely poled currents to the upper windings of relays Rs and Rv. rihe interconnecting circuit includes the upper winding of relay Rs, the upper armature and make contact of relay R5, the lower innermost armature and make contact of relay R5, the operating circuit of the selector NTS (not shown) and the upper windings of relays Rs and R7 which are connected to the armature `of relay Rs and its marking contact M. The relays Re and R7 will move their armatures between their marking and spacing contacts M and S in accordance with the signals transmitted ,from the subscribers oflice and thereby connect oppositely poled batteries to the midpoints of the windings of the relay Re. These oppositely poled batteries will cause oppositely directed currents to flow over the line La to the distant subscribers station or central oliice (not shown).

During signaling from the subscribers oiiice to the circuit connected to the line L3 the neutralizing wire L2 will again perform its neutralizing functions to eliminate the effects of transient and extraneous voltages and the lamp P2 will indicate to the subscriber that his circuit is connected to the line La and that the subscribers cir-cuit is not transmitting signals into the air. This is an important feature of this arrangement not only because it indicates that the subscribers oflice and the line L3 are interconnected but also because the indication is continuous and is interrupted only when the interconnecting circuit is broken.

While this invention has been shown and described in certain particular arrangements merely for the purpose of illustration, it will be understood that the genera-l principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In a telegraph system, the combination of a subscribers station, a central ofce, a telegraph line over which telegraph signals may be transmitted, a neutralizing line which together with the telegraph line are interposed between the subscribers station and the central oflice, the neutralizing line picking up extraneous voltages similar to those picked up by the telegraph line, means coupled to said lines whereby said extraneous voltages may be effectively nulliiied, a relay at the subscribers oilice, the winding of said relay being connected to the neutralizing line, an indicating device controlled by said relay, and means at the central oflioe for applying voltages to said neutralizing line to energize said relay.

2. In a telegraph system, the combination of two separated stations, a telegraph line, a neutralizing line which together withsaid telegraph line span the two stations, means connected to said lines for the neutralization of extraneous voltages, means for indicating whether or not signaling may take place between said stations over said telegraph line, said means including a relay the winding of which is connected in series with said neutralizing line, an indicating device controlled by said relay, and means for applying voltage to said neutralizing line to operate said relay without interfering with signaling over said telegraph line.

3. In a telegraph system, the combination of first and second stations, a line over which telegraph signals may be transmitted, a neutralizing wire, said neutralizing wire and said line running parallel to each other between said two stations, means connected to said line and said wire for the neutralization of extraneous voltages, a relay at the rst station having its Winding connected in series with said neutralizing wire, a device at said rst station having an impedance substantially equal to'that of said relay winding and connected in series with said line, an indicating device controlled by said relay, and means at said second station for applying voltage to said neutralizing wire to operate said relay.

4. In a telegraph system, a first subscribers station, a central oce, a second subscribers station connected to said central oiiice, a telegraph line over which telegraph signals may be transmitted, an auxiliary line running parallel to said telegraph line, said telegraph line and said auX- iliary line interconnecting the rst subscribers station and said central olce, means connected to said lines for the neutralization of extraneous voltages, a relay at said rst subscribers station having its Winding in series With said auxiliary line, an indicating device controlled by said relay, and means responsive to a predetermined signal from said second subscribers station to indicate at the first subscribers station whether or not the two subscribers stations may send telegraph signals to each other over the telegraph line, said means including apparatus at the central oiice responsive to said predetermined signal to apply voltage to said auxiliary line to operate said relay.

5. In a telegraph system, the combination of move the voltage of said source from said neutralizing line to indicate to the operator at said iirst station that telegraph signals may be transmitted over said telegraph line, and means responsive to a second predetermined signal at said second station to apply said voltage to said neutralizing line to indicate to the operator at said rst station that telegraph signals may not be transmitted over said telegraph line.

6. In a telegraph system, the combination of a first subscribers station, a central oiiice, a second subscribers station connected to said central oihce, a line for telegraph signals, a neutralizing conductor which together with said line run substantially parallel to each other between the first subscribers station and said central oice, means connected to said line and said conductor for neutralizing extraneous voltages, an indicating device at said rst subscribers station controlled by voltage received over said neutralizing conductor from said central oice, a source of voltage for connection to said neutralizing line, means responsive to a predetermined signal received at said central oice from said second subscribers station to effectively connect said rst and second subscribers stations through said central office so that telegraph signals may be transmitted between said stations over said line, said means also including means to remove the voltage of said source from said neutralizing conductor, and means responsive to a different predetermined signal received at the central oiice from said second subscribers station to effectively disconnect said stations from each other and simultaneously apply said voltage to the neutralizing conductor to thereby operate said indicating device.

ROBERT JAMES EGNER. CHARLES ROBERT WALKER. 

